Mining in the catchment

Mining in the catchment

Longwall mining

There is a long history of longwall mining in the drinking water catchments. Longwall mining is a form of underground coal mining where a substantial panel of coal is progressively extracted by a large shearing machine and the resulting void is then allowed to collapse behind it.

Longwall mining causes subsidence at depth and at the land surface, and this subsidence and its associated fracturing of the rocks overlying the mined voids can potentially damage infrastructure and cause losses from water storages and streams and may also impact on ecological integrity of overlying swamps and catchments.

WaterNSW engaged a team of specialist consultants to compile a literature review of the processes and potential impacts arising from Underground Mining Beneath Catchments and Water Bodies (PDF, 27428.4 KB). There are three potential water loss mechanisms identified in this study which may occur due to mining-induced surface subsidence. These three mechanisms are conceptualised in diagrams – showing the situation in a simplified Southern Coalfields setting, before and after mining.

At present, two mining companies have active longwall coal mining operations under the Metropolitan Special Area that surrounds the Cataract, Cordeaux, Avon and Nepean Dams, and the Woronora Special Area that surrounds Woronora Dam.

Coal seam gas

There are currently no licences or leases in place in the Special Areas that permit coal seam gas activities. This is an outcome from a 2015 decision by the NSW Government to buy back the few licenses applying to parts of the Special Areas.

In November 2013, the NSW Government placed a hold on exploration and extraction of coal seam gas in the Special Areas, pending an investigation by the NSW Chief Scientist and Engineer into the impact of coal seam gas activities and other contributing factors on water in the Special Areas.

In placing the hold on coal seam gas activities, the NSW Government noted the role of the Special Areas in protecting the water supply.

In 2014, the Independent Planning Commission (IPC, then PAC) rejected a proposal by APEX Energy to conduct coal seam gas exploration in the Woronora catchment and Special Area. In rejecting the proposal, the PAC noted the importance of the Special Areas and the uncertainty about the impacts of coal seam gas.